Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
2000-08-11
2001-10-30
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C307S135000, C307S147000, C361S058000, C710S108000
Reexamination Certificate
active
06310410
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to computer plug-ins and more particularly to a method and apparatus for reducing source voltage deviation in hot plug applications.
BACKGROUND OF THE INVENTION
Hot plug devices offer flexibility for adding function boards to a main system while the system is operating. Hot plug systems refer to systems that may receive additional plug-in devices without terminating power to the system.
A problem with hot plug systems is that input capacitors on the device to be plugged in, which is commonly referred to as a function board, draw a large amount of current from a voltage source located on the main system. This current is commonly referred to as in-rush current. A large current in-rush creates source voltage deviation, which is sometimes referred to as “undershoot.” Undershoot may cause malfunctioning of the main system.
A prior method for addressing this problem utilizes an in-rush current limiter in series with the in-rush current. The in-rush current limiter is implemented by a negative temperature characteristic resistor. During hot plug-ins, the initial resistance of the negative temperature characteristic resistor is large, and the in-rush current generates heat in the resistor. This generated heat reduces the resistance of the negative temperature characteristic resistor to an operating resistance that is determined by the normal operating current. This method is somewhat suitable for low current applications. However, for high current applications, the operating resistance in the negative temperature characteristic resistor is too high and causes significant power loss. Furthermore, for either type of application, negative temperature characteristic resistors are expensive, increasing the cost of systems utilizing such resistors.
SUMMARY OF THE INVENTION
Accordingly, a need has arisen for an improved method and apparatus for reducing source voltage deviation in hot plug applications. The present invention provides an apparatus and method for reducing source voltage deviation in hot plug applications that address shortcomings of prior systems and methods.
According to one embodiment of the invention, a hot swappable system includes a first system having an electrically conductive projection and a second system. The second system includes a voltage source having a first node having a first polarity, a resistive element, and a receptor system associated with the first node and configured to receive insertion of the conductive projection. The receptor system includes first and second conductive contacts electrically connected by the resistive element. The first conductive contact is disposed relative to the second conductive contact such that insertion of the conductive projection into the receptor system causes sequential electrical contact between the conductive projection and the first contact and then between the conductive projection and the second contact.
According to another embodiment of the invention, a method for connecting a plug-in device having a conductive projection to a base system to reduce deviation of a source voltage on the base system includes providing first, second, and third electrical contacts on the base system. The method also includes providing a voltage source between the second electrical contact and the third electrical contact. A resistive element is connected between the first and second electrical contacts and the conductive projection is electrically connected to the first electrical contact such that the current flows from the voltage source to the resistor to the conductive projection. After electrically connecting the conductive projection to the first electrical contact, the conductive projection is electrically connected to the second electrical contact such that the current flows from the voltage source through the second electrical contact to the conductive projection but that no substantial current flows from the voltage source through the resistor to the conductive projection.
Embodiments of the invention provide numerous technical advantages. For example, in one embodiment of the invention, the in-rush current due to hot plug in of a function board is substantially reduced resulting in substantially reduced source voltage deviation. Reduced source voltage deviation leads to more reliable operation of the main system. These advantages may be realized in some embodiments with only minor cost increases to systems incorporating the teachings of the present invention.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.
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Dai Heping
Daniels David G.
Lin Feng
Brady W. James
Fleming Fritz
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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